Honeycomb-like g-C3N4/CeO2-x nanosheets obtained via one step hydrothermal-roasting for efficient and stable Cr(VI) photo-reduction

Graphitic carbon nitride (g-C₃N₄)-based materials are regarded as one of the most potential photocatalysts for utilizing solar energy. In this work, we reported a facile one step in-situ hydrothermal-roasting method for preparing honeycomb-like g-C₃N₄/CeO₂ nanosheets with abundant oxygen vacancies (g-C₃N₄/CeO_2-x). The hydrothermal-roasting and incomplete-sealed state can (i) generate an in-situ reducing atmosphere (CO, N₂, NH₃) to tune the concentration of oxygen vacancies in CeO₂; (ii) beneficial to prevent continuous growth of g-C₃N₄ and results in honeycomb-like g-C₃N₄/CeO_2-x hybrid nanosheets. What is more, the g-C₃N₄/CeO_2-x photocatalyst exhibited extended photoresponse range, increased specific surface area and obviously enhanced separation efficiency of photogenerated electron-hole pairs. As a proof-of-concept application, the optimized g-C₃N₄/CeO_2-x nanosheets could achieve 98% removal efficiency for Cr(VI) under visible light irradiation (λ ≥ 420 nm) within 2.5 h, which is significantly better than those of pure g-C₃N₄ and CeO₂. This work provides a new idea for more rationally designing and constructing g-C₃N₄-based catalysts for efficient extended photochemical application.     

Upgraded charge transport in g-C3N4 nanosheets by boron doping and their heterojunction with 3D CdIn2S4 for efficient photodegradation of azo dye

The facilitation of charge transport toward the targeted chemical reaction is a challenging task for two-dimensional (2D) nanomaterials. We demonstrate the effectiveness of two different strategies, non-metal doping and heterojunction formation, to adjust the electronic and molecular structures of g-C₃N₄ nanosheets (CN), which could widen the visible-light response and improve the photo-induced electron–hole separation. The g-C₃N₄ nanosheets containing impurity levels (boron doping (BCN)) were prepared by a high-temperature solid-state reaction. Additionally, by anchoring the 3D dichalcogenide structures (CdIn₂S₄) elicited by a wet chemical route, hybrid BCN/CdIn₂S₄ nanostructures were obtained. The resulting BCN/CdIn₂S₄ (BCN–CIS3) nanostructures exhibited an excellent degradation efficiency (95%) for methyl orange (MO) compared to pristine g-C₃N₄ nanosheets (CN) (28%) and boron-doped g-C₃N₄ (BCN) (35%). All the optimized photocatalysts were thoroughly characterized using various techniques and investigated for comparative structural, optical, morphological, and catalytic properties. Our results reveal that introducing boron atoms into the lattice of g-C₃N₄ nanosheets leads to reduction in the band-gap energy and rapid electron transfer. The formation of heterojunctions with the 3D CdIn₂S₄ further assists in improving the degradation efficiency by minimizing the undesired electron–hole recombination, as confirmed by time-resolved photoluminescence (TRPL) analysis. This work proposes feasible strategies and their synergy to develop innovative materials for sustainable energy conversion and environmental remediation applications.     

Water Transport with Ultralow Friction through Partially Exfoliated g-C3N4 Nanosheet Membranes with Self-Supporting Spacers

Two-dimensional (2D) graphitic carbon nitride (g-C₃N₄) nanosheets show brilliant application potential in numerous fields. Herein, a membrane with artificial nanopores and self-supporting spacers was fabricated by assembly of 2D g-C₃N₄ nanosheets in a stack with elaborate structures. In water purification the g-C₃N₄ membrane shows a better separation performance than commercial membranes. The g-C₃N₄ membrane has a water permeance of 29 L m⁻² h⁻¹ bar⁻¹ and a rejection rate of 87 % for 3 nm molecules with a membrane thickness of 160 nm. The artificial nanopores in the g-C₃N₄ nanosheets and the spacers between the partially exfoliated g-C₃N₄ nanosheets provide nanochannels for water transport while bigger molecules are retained. The self-supported nanochannels in the g-C₃N₄ membrane are very stable and rigid enough to resist environmental challenges, such as changes to pH and pressure conditions. Permeation experiments and molecular dynamics simulations indicate that a novel nanofluidics phenomenon takes place, whereby water transport through the g-C₃N₄ nanosheet membrane occurs with ultralow friction. The findings provide new understanding of fluidics in nanochannels and illuminate a fabrication method by which rigid nanochannels may be obtained for applications in complex or harsh environments.     

Defects Promote Ultrafast Charge Separation in Graphitic Carbon Nitride for Enhanced Visible-Light-Driven CO2 Reduction Activity

Fundamental photocatalytic limitations of solar CO₂ reduction remain due to low efficiency, serious charge recombination, and short lifetime of catalysts. Herein, two-dimensional graphitic carbon nitride nanosheets with nitrogen vacancies (g-C₃N_x) located at both three-coordinate N atoms and uncondensed terminal NH_x species were prepared by one-step tartaric acid-assistant thermal polymerization of dicyandiamide. Transient absorption spectra revealed that the defects in g-C₃N₄ act as trapped states of charges to result in prolonged lifetimes of photoexcited charge carriers. Time-resolved photoluminescence spectroscopy revealed that the faster decay of charges is due to the decreased interlayer stacking distance in g-C₃N_x in favor of hopping transition and mobility of charge carriers to the surface of the material. Owing to the synergic virtues of strong visible-light absorption, large surface area, and efficient charge separation, the g-C₃N_x nanosheets with negligible loss after 15 h of photocatalysis exhibited a CO evolution rate of 56.9 μmol g⁻¹ h⁻¹ under visible-light irradiation, which is roughly eight times higher than that of pristine g-C₃N₄. This work presents the role of defects in modulating light absorption and charge separation, which opens an avenue to robust solar-energy conversion performance.     

g-C3N4/Ag/TiO2复合材料的构筑及其光催化性能（英文）

以合成的g-C3N4纳米片和Ag/TiO2空心微球为原料,采用机械搅拌的方法构筑了g-C3N4/Ag/TiO2三元复合光催化剂。采用X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、扫描电镜(SEM)、X射线光电子能谱(XPS)、紫外-可见光漫反射(UV-Vis DRS)和光致发光光谱(PL)对g-C3N4/Ag/TiO2进行了表征。研究表明,g-C3N4/Ag/TiO2是由Ag/TiO2微球和g-C3N4纳米片复合而成的。与TiO2相比,其可见光响应范围延长,光生载流子的分离速率加快。在室温下,用降解罗丹明B的反应考察了g-C3N4/Ag/TiO2的可见光催化活性。研究表明,光照180 min时,g-C3N4(0.5%)/Ag/TiO2显示了最高的光催化活性(91.9%),分别是TiO2和Ag/TiO2的7.5和1.8倍。光催化活性的提高与合理的异质结构建和Ag的导电性能有关。     

A carbon-rich g-C3N4 with promoted charge separation for highly efficient photocatalytic degradation of amoxicillin

A novel carbon-rich g-C₃N₄ nanosheets with large surface area was prepared by facile thermal polymerization method using urea and 1,3,5-cyclohexanetriol. Plenty of carbon-rich functional groups were introduced into the surface layers of g-C₃N₄, which constructed the built-in electric field (BIEF) and resulted in improved charge separation; therefore, the carbon-rich g-C₃N₄ displayed superior photocatalytic activity for amoxicillin degradation under solar light. The contaminant degradation mechanism was proposed based on radical quenching experiments, intermediates analysis and density functional theory (DFT) calculation. Moreover, the reusing experiments showed the high stability of the material, and the amoxicillin degradation under various water matrix parameters indicated its high applicability on pollutants treatment, all of which demonstrated its high engineering application potentials.     

Facile synthesis of GO as middle carrier modified flower-like BiOBr and C3N4 nanosheets for simultaneous treatment of chromium(VI) and tetracycline

A novel GO modified g-C₃N₄ nanosheets/flower-like BiOBr hybrid photocatalyst is fabricated by a facile method. The characterization results reveal that wrinkled GO is deposited between g-C₃N₄ nanosheets and flower-like BiOBr forming a Z-scheme heterojunction. As a mediator, plicate GO plays a positive role in prompting photogenerated electrons transferring through its sizeable 2D/2D contact surface area. The g-C₃N₄/GO/BiOBr hybrid displays a superior photocatalytic ability to g-C₃N₄ and BiOBr in photodegrading tetracycline (TC), whose removal efficiency could reach 96% within 2 h. Besides, g-C₃N₄/GO/BiOBr composite can reduce Cr(VI), and simultaneously treat TC and Cr(VI) combination contaminant under the visible light. The g-C₃N₄/GO/BiOBr ternary composite also exhibits satisfactory stability and reusability after four cycling experiments. Further, a feasible mechanism related to the photocatalytic process of g-C₃N₄/GO/BiOBr is put forward. This study offers a ternary hybrid photocatalyst with eco-friendliness and hopeful application in water pollution.     

Gold/monolayer graphitic carbon nitride plasmonic photocatalyst for ultrafast electron transfer in solar-to-hydrogen energy conversion

Gold (Au) plasmonic nanoparticles were grown evenly on monolayer graphitic carbon nitride (g-C₃N₄) nanosheets via a facile oil-bath method. The photocatalytic activity of the Au/monolayer g-C₃N₄ composites under visible light was evaluated by photocatalytic hydrogen evolution and environmental treatment. All of the Au/monolayer g-C₃N₄ composites showed better photocatalytic performance than that of monolayer g-C₃N₄ and the 1% Au/monolayer g-C₃N₄ composite displayed the highest photocatalytic hydrogen evolution rate of the samples. The remarkable photocatalytic activity was attributed largely to the successful introduction of Au plasmonic nanoparticles, which led to the surface plasmon resonance (SPR) effect. The SPR effect enhanced the efficiency of light harvesting and induced an efficient hot electron transfer process. The hot electrons were injected from the Au plasmonic nanoparticles into the conduction band of monolayer g-C₃N₄. Thus, the Au/monolayer g-C₃N₄ composites possessed higher migration and separation efficiencies and lower recombination probability of photogenerated electron-hole pairs than those of monolayer g-C₃N₄. A photocatalytic mechanism for the composites was also proposed.     

溶液法剥离的氮化碳在各种衬底上分散的AFM研究

石墨相氮化碳(g-C_3N_4)因为其特殊的层状结构及电子性质在催化和光催化领域里受到广泛关注和研究。本文以异丙醇及异丙醇-水混合溶液为介质对g-C_3N_4粉末进行超声液相剥离,并利用原子力显微镜详细表征了剥离后的溶液分散至云母、高定向热解石墨(HOPG)、Au(111)等不同衬底表面的结果。发现溶液经10h超声后,g-C_3N_4被剥离成尺寸约100nm左右的扁平颗粒,但无法形成完美的超薄层结构。这可能是由于经热聚合法合成的g-C_3N_4本身晶化程度较低所致。     

Two-dimensional g-C3N4 nanosheets-based photo-catalysts for typical sustainable processes

Graphitic carbon nitride (g-C₃N₄) has been widely studied as a visible light responsive photocatalyst in recent years, due to its facile synthesis, low cost, high stability, and appropriate bandgap/band positions. In this review, we firstly introduce and compare various exfoliation approaches of bulk g-C₃N₄ into ultrathin g-C₃N₄ nanosheets. Then, many modification strategies of g-C₃N₄ nanosheets are also reviewed, including heterojunction construction, doping, defect control, and structure design. Thereafter, the charge transfer mechanism in g-C₃N₄ nanosheets based heterojunctions is present, e.g., Z-scheme, S-scheme and other forms. Besides, the photocatalytic applications of g-C₃N₄ nanosheets based photocatalysts are summarized including environmental remediation, energy generation and storage, organic synthesis, and disinfection. This review ends with a summary and some perspectives on the challenges and new directions in exploring g-C₃N₄ nanosheets-based photocatalysts.     

Fe doped g-C3N4 composited ZnIn2S4 promoting Cr(VI) photoreduction

30% FeCN/ZIS (30% Fe doped g-C₃N₄ composited ZnIn₂S₄) was synthesized by a simple water bath method, via in-situ growth of abundant well-dispersed ZnIn₂S₄ nanosheets on the Fe doped g-C₃N₄ surface. Experimental results showed the optimized 30% FeCN/ZIS achieved the best photoreduction of Cr(VI) performance within a wide pH range, which was 9.5 times and 700 times higher than that of pure ZnIn₂S₄ and 30% FeCN (Fe doped g-C₃N₄). This is due to the intense synergy between the Fe-N_x bond and close interface contact produces a high-speed charge transfer channel, thus significantly improving the efficiency of optical carrier separation and migration. Meanwhile, UV-vis diffuse reflection spectra and photoluminescence spectroscopy showed that iron doping significantly narrowed the bandgap of g-C₃N₄, preventing electron-hole pair recombination. Further, the microstructures and charge separation properties were analyzed by scanning electron microscope, Photoluminescence Spectroscopy and time-resolved photoluminescence, which revealed the structure-activity relationship of composite structure and the synergistic mechanism of each functional component. This research should provide a viable technique for creating composites with high photocatalytic activity for the treatment of chromium-containing wastewater.     

Cascaded electron transition proved by femto-second transient absorption spectroscopy for enhanced photocatalysis hydrogen generation

Regulating flow direction of photo-excited electrons from interior to active sites in surface is critical to enhance the photocatalytic performance. Herein, photoinduced chemical reduction process was utilized to pinpoint deposit CdS and NiS nanodots sequentially onto g-C₃N₄ nanosheets. The resulted hybrid composite NiS/CdS/g-C₃N₄ was much more active under visible light, and eventually boosted the hydrogen evolution rate of 3015 μmol g^?1 h^?1, to be 2.4 folds better than that of g-C₃N₄. Because of the relative low content of CdS (around 3.0 wt%), the enhanced activity is due to the favoring band overlapping and promoting charge separation rather than increasing light absorption. Femto-second time-resolved transient absorption spectroscopy (fs-TAS) clearly reveals that the photo-excited electrons are from g-C₃N₄, and then migrate unidirectionally to CdS and finally to NiS, which is caused by the precisely regulate the position of CdS and NiS on g-C₃N₄ surface. This study elucidates the electron transfer kinetics and processes in multi-component system and affords a new avenue to construct stable photocatalysts with high activity.     

g-C3N4基复合分离膜的制备及光催化性能

利用g-C₃N₄纳米片表面的氨基与膜基底材料氯甲基化聚醚砜（CMPES）的苄氯基团发生化学交联反应,再通过相转化法制备出g-C₃N₄/CMPES复合膜。系统研究了g-C₃N₄纳米片的添加对复合膜的结构、形貌及过滤、光催化、抗污染性能的影响,并探讨其光催化降解牛血清白蛋白溶液（BSA）的机理。研究结果表明：g-C₃N₄纳米片与膜基底材料通过化学键相连接,有效提高了复合膜的光催化性能和稳定性。由于g-C₃N₄纳米片的亲水性和光催化作用,使复合膜表现出优异的过滤性能和抗污染性能。     

Fast electron transfer and enhanced visible light photocatalytic activity by using poly-o-phenylenediamine modified AgCl/g-C3N4 nanosheets

Exfoliation of bulk graphitic carbon nitride (g-C₃N₄) into two-dimensional (2D) nanosheets is one of the effective strategies to improve its photocatalytic properties so that the 2D g-C₃N₄ nanosheets (CN) have larger specific surface areas and more reaction sites. In addition, poly-o-phenylenediamine (PoPD) can improve the electrical conductivity and photocatalytic activity of semiconductor materials. Here, the novel efficient composite PoPD/AgCl/g-C₃N₄ nanosheets was first synthesized by a precipitation reaction and the photoinitiated polymerization approach. The obtained photocatalysts have larger specific surface areas and could achieve better visible-light response. However, silver chloride (AgCl) is susceptible to agglomeration and photocorrosion. The PoPD/AgCl/CN composite exhibits an extremely high photocurrent density, which is three times that of CN. Obviously enhanced photocatalytic activities of PoPD/AgCl/g-C₃N₄ are revealed through the photodegradation of tetracycline. The stability of PoPD/AgCl/CN is demonstrated based on four cycles of experiments that reveal that the degradation rate only decreases slightly. Furthermore, ?O₂^? and h⁺ are the main active species, which are confirmed through a trapping experiment and ESR spin-trap technique. Therefore, the prepared PoPD/AgCl/CN can be considered as a stable photocatalyst, in which PoPD is added as a charge carrier and acts a photosensitive protective layer on the surface of the AgCl particles. This provides a new technology for preparing highly stable composite photocatalysts that can effectively deal with environmental issues.     

Synthesis and characterization of g-C3N4/BiVO4 composite photocatalysts with improved visible-light-driven photocatalytic performance

Novel visible-light-driven g-C₃N₄/BiVO₄ composite photocatalysts were fabricated via sol–gel and simple mixing and heating methods. The photocatalysts were characterized by X-ray diffraction, thermogravimetric, Fourier transform infrared, transmission electron microscope, Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy, diffuse reflectance spectroscopy, and photoluminescence spectra. The results indicated that BiVO₄ was well dispersed on g-C₃N₄ sheet and an interaction between g-C₃N₄ and BiVO₄ was confirmed, which were facile to the electron transfer from g-C₃N₄ to BiVO₄ species. The mechanism was further induced to the heterojunction effect to improve the photocatalytic efficiency. The g-C₃N₄/BiVO₄ heterojunction at a weight ratio of 80 % calcined at 500 °C exhibited the most excellent photocatalytic ability for RhB decolorization under visible-light irradiation (λ > 420 nm) which was extraordinary more active than that of pure components.     

Exited State Absorption Upconversion Induced by Structural Defects for Photocatalysis with a Breakthrough Efficiency

The nitrogen-deficient graphitic carbon nitride (g-C₃N₄) has been prepared, a new excited state absorption (ESA) up-conversion mode is discovered, which is directly induced by structural defects, showing distinct chemical characteristics from those based on lanthanide ions and triplet states chromophores. The abundant N_2C vacancies in g-C₃N₄ nanosheets work as the crucial intermediate excitation states, which lead to g-C₃N₄ upconverted emitting at the wavelength of 436 nm excited by the light with the wavelength of 800 nm. This process is proven to proceed via a two-photon involved ESA mode with a breakthrough quantum efficiency of 0.64 %. Further, we combine N_2C vacancies enriched g-C₃N₄ with In₂S₃ and CdS, and successfully achieved an infrared light driven photocatalytic reactions. These findings offered a new family of up-conversion materials; more semiconductors with various structural defects are potential complementary members.     

氮缺陷石墨相氮化碳的制备及其光催化降解环境有机污染物性能

通过在三聚氰胺热分解过程中加入NaHCO₃制备出具有氮缺陷的石墨相氮化碳（g-C₃N₄）,利用X射线衍射（XRD）、傅里叶变换红外光谱（FT-IR）、N₂吸附-脱附、X射线光电子能谱（XPS）、紫外-可见漫反射光谱（UV-vis DRS）和固体荧光光谱（PL）等方法对其进行表征,并在可见光（λ> 420nm）照射下,以水相中罗丹明B（RhB）的降解为模型反应,研究了该氮缺陷g-C₃N₄对有机污染物降解的光催化活性。结果表明,引入氮缺陷可以提高g-C₃N₄对可见光的吸收以及电子-空穴对的分离效率,进而提高g-C₃N₄的可见光催化活性。催化剂CNK0.005、CNK0.01和CNK0.05在30min内对RhB的降解率分别为79.8%、100.0%和87.6%;而在相同条件下,没有氮缺陷的g-C₃N₄对RhB的降解率仅为59.8%。     

Enhanced photoelectrochemical performance of P-doped g‑C3N4/Zn0.5Cd0.5S heterojunction photocathode for water splitting

Photoelectrochemical (PEC) hydrogen evolution reaction at semiconductor photocathode in the presence of visible light is a promising way to harvest renewable energy. Graphitic carbon nitride (g-C₃N₄) has intriguing properties, making it highly favorable for photoelectrode engineering. This work demonstrated P-doped g-C₃N₄ nanosheets (PCN-Nss) and Zn_0.5Cd_0.5S heterojunction (PCN-Nss/ZCS-40) for PEC hydrogen evolution reaction using simulated sunlight. A facile and simple two-step strategy developed PCN-Nss/ZCS-40 photocathode; including co-precipitation of ZnCdS in the highly dispersed suspension of PCN-Nss and then drop-casting it on the surface of a conductive substrate. The intimate contact between PCN-Nss and ZnCdS at the molecular level due to the formation of heterojunction efficiently triggers charge separation, suppressing electron-hole pair recombination and easing the movement of photo-generated holes towards the conductive substrate. PCN-Nss/ZCS-40 (40% P-C₃N₄ by weight) showed substantially improved photocurrent response (?12 µA cm^?2) at ?0.6 V vs Ag/AgCl reference electrode in 0.2 M Na₂S solution, which is almost 40 times greater than simple P-C₃N₄ nanosheets under the same conditions. This work will expose new applications for P-doped graphitic carbon nitride-based heterostructures for PEC water splitting.     

Pt/g-C_3N_4/KB纳米复合催化剂的制备及其甲醇氧化性能

采用溶液中等离子放电法制备出了Pt纳米颗粒,用热氧化刻蚀和水热法成功的对石墨相氮化碳(g-C_3N_4)进行处理进而均匀吸附在科琴黑(KB)表面,最终制备出了Pt/g-C_3N_4/KB纳米复合催化剂。通过XRD分析,扫描电镜,透射电镜和电化学工作站探究了催化剂的组成、结构、颗粒大小以及电化学性能。Pt/g-C_3N_4/KB纳米复合催化剂展现出了良好的甲醇电氧化性能,性能的提升可能是由于g-C_3N_4良好的化学稳定性,N元素的存在改变Pt外层电子结构从而提高催化活性,这些因素提高了Pt的催化效率。     

Enhanced oxidase-like activity of g-C3N4 nanosheets supported Pd nanosheets for ratiometric fluorescence detection of acetylcholinesterase activity and its inhibitor

The undesirable enzymatic activity of nanozymes under near neutral p H condition and the traditional single signal output always restrict the analytical application of nanozyme-based biosensors.Herein,graphitic carbon nitride nanosheets supported palladium nanosheets composite （Pd/g-C₃N₄） with both oxidase-like activity and fluorescent property is synthesized.Notably,Pd/g-C₃N₄exhibits enhanced oxidase-like activity compared to Pd NSs under p H 7.4.By c...